This invention relates in general to the manufacture of slip joints, such as are commonly used in vehicle drive train systems, for transmitting rotational force or torque between axially movable components. In particular, this invention relates to an improved structure for a cage for maintaining the balls in a rolling ball spline type of slip joint in a spaced apart relationship.
Drive train systems are widely used for transferring power from a power source to a driven mechanism. Frequently, the power source generates rotational power, and such rotational power is transferred from the power source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Not only must a typical drive train system accommodate a limited amount of angular misalignment between the source of rotational power and the rotatably driven device, but also typically it must accommodate a limited amount of relative axial movement therebetween. For example, in most vehicles, a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the vehicle is operated. To address this, it is known to provide a slip joint in the driveshaft assembly. A typical slip joint includes first and second members that have respective structures formed thereon that cooperate with one another for concurrent rotational movement, while permitting a limited amount of axial movement to occur therebetween. Two types of slip joints are commonly used in conventional driveshaft assemblies, namely, a sliding spline type and a rolling ball spline type.
A typical rolling ball spline type of slip joint includes male and female members having respective pluralities of longitudinally extending grooves formed thereon. The male member is generally cylindrical in shape and has a plurality of inwardly extending grooves formed in the outer surface thereof. The male member may be formed integrally with or secured to an end of the driveshaft assembly described above. The female member, on the other hand, is generally hollow and cylindrical in shape and has a plurality of outwardly extending grooves formed in the inner surface thereof. The female member may be formed integrally with or secured to a yoke that forms a portion of one of the universal joints described above. To assemble the slip joint, the male member is inserted within the female member such that the inwardly extending grooves of the male member are aligned with the outwardly extending grooves of the female member. A plurality of torque transfer balls is disposed in each of the aligned pairs of the grooves. As a result, the male and female members are connected together through the torque transfer balls for concurrent rotational movement. However, the male member can slide relative to the inwardly extending splines of the female member to allow a limited amount of relative axial movement to occur between the engine/transmission assembly and the axle assembly of the drive train system.
Typically, a rolling ball spline slip yoke includes a cage or retainer that extends between the male and female members and maintains the balls disposed in each of the aligned pairs of the grooves in a spaced apart relationship from one another. Thus, the cage is provided to prevent adjacent ones of these balls from engaging one another during relative axial movement of the male and female members. It has been found that such engagement of the balls during relative axial movement of the male and female members can adversely affect the operation of the rolling ball spline slip yoke. However, known cage structures have been found to be relatively complicated in structure and expensive to manufacture. Thus, it would be desirable to provide an improved structure for such a cage that is relatively simple in structure and inexpensive to manufacture.